The present invention relates to apparatus for supporting and guiding a moving web in tension and, more particularly, to apparatus to be used in a spaced combination of two for supporting a roll and providing a signal output reflecting force on the roll at the points of support comprising, a coupling for fixed attachment to a shaft (live carrying a roll fixedly attached thereto or stationary carrying a roll on bearings supported thereon) or a live roll; at least one resiliently bendable beam supported at one end by a support member and extending therefrom to resiliently support the coupling; a self aligning ball bearing being disposed between the coupling and the beam; pivot pin means interconnecting, when installed, the coupling and the support member to prevent relative rotation thereof about the shaft or roll axis while permitting pivotal movement normal to that axis; and means to provide signals representing web tension forces transmitted to the beam(s), the coupling and support member being capable of relative rotation when the pivot pin means is not installed.
Tension transducers are well known in the art and are manufactured and sold commercially by a number of companies including the applicant's company, Dover Flexo Electronics, Inc. A web tension transducer is used to measure tension in any moving web. The output signal produced can be displayed for manual control of the tension or can be used for automated control. They are typically used in printing presses, coaters, laminators, textile machines, slitter-rewinders, sheeters, papermaking machines, and any other machines which in some way processes a continuous web of paper, plastic film, metal, textile, non-woven textile, felt, rubber, or any combination of the foregoing. Variations of web tension can cause web breakage, slack web, wrinkling, curling, stretching, and in general, poor quality product and excessive waste. These problems can be eliminated by proper control of web tension. The basis of proper control is tension measurement. The basis of measurement is a transducer which will convert a force (web tension) into an electrical signal which can be used for control purposes. The transducer must be accurate regardless of web speed and tension or it will not allow the correction of the aforementioned problems.
Prior art tension transducers are typified by U.S. Pat. No. 4,691,579 issued to applicant herein, entitled TENSION TRANSDUCER, and assigned to the assignee of this invention, the transducer is incorporated into a supportive joint used to support a rotating or nonrotating shaft having the roll over which the web is moving mounted thereof. The joints are used in pairs one at each end of the roll.
This prior art transducer is of a cantilevered beam type wherein a force to be measured is applied perpendicularly to the end of the beam through the joint and the improved joint comprises a self-aligning first roller bearing having an axially aligned center bore and a cylindrical outer surface. A cylindrical inner member is carried by the end of the beam while a cylindrical outer member is provided having cylindrical inner and outer surfaces. The cylindrical inner surface is of a diameter to be a sliding fit about the outer surface of the first roller bearing and has parallel, spaced, inward facing ridges thereon of a spacing greater than the width of the first roller bearing. A biasing device urges the first roller bearing toward a neutral position. A second roller bearing having a center bore with a radius larger than the radius of the cylindrical outer surface of the cylindrical outer member is disposed concentrically thereabout in alignment with the first roller bearing. There is a device for non-movably supporting the second roller bearing with respect to the cantilevered beam. The force receiving device comprises a cylindrical bushing for receiving a shaft to be supported by the first roller bearing.
When this prior art transducer is used with a live roll mounted by bearings on what is intended to be a stationary shaft, that shaft will often rotate in the self-aligning bearing about the roll axis. This is detrimental to the performance of the transducer and the roll if the shaft is not straight and/or balanced. Further stationary shafts tend to be lighter than those which are intended to carry loads while rotating and thus subject to bending.
Wherefore, it is the object of the present invention to provide a convertible web tension transducer for web support and tension measurement which can be readily adapted for use with live shafts carrying rolls, stationary shafts carrying live rolls and directly with live rolls, which when used with stationary shafts carrying live rolls does not exhibit the disadvantages attendant undesired rotation of such shafts that was possible with the prior art transducer of U.S. Pat. No. 4,691,579.
It is another object of the present invention to provide a web tension transducer having a simple inexpensive means for adapting the transducer to the different uses.
Other objects and benefits of the present invention will become apparent from the description contained hereinafter taken in conjunction with the drawing figures which accompany it.